While document copiers have become prolific, there are certain situations where it becomes highly desirable to prevent the copying of specific originals. Such situations could occur, for example, with the illicit or unauthorized photocopying of classified or proprietary documents.
The problem of illicit photocopying of classified or proprietary documents has become pandemic. It would be highly desirable to be able to inhibit the xerographic or other type reproduction of sensitive documents. To do so requires that the photocopier be equipped with a detection and control system that will inhibit the copier automatically before the image can be captured electrostatically, unless a proper "enable" signal is received. This becomes especially important when the frequent occurrence of government espionage activities is considered in which illicit photocopies have been made of very highly classified documents. Recently, there have been a number of publicly reported cases wherein copies of information regarding battle plans, fleet dispositions, communication frequencies, corporate strategies, merger plans, sales histories/forecasts, new product development reports, etc., have been sold on the open market. The ability to prevent the unauthorized photocopying of selected documents becomes extremely important to both national security and the potential future of many corporate activities and entities.
One solution to this problem is disclosed in copending application Ser. No. 868,983, filed 5-30-86, assigned to the same assignee, now U.S. Pat. No. 4,678,322 wherein unique phosphors are applied to paper. The phosphors may be applied either to the surface of the paper in a post production facility, or incorporated into the paper during the last stages of paper manufacture. Another solution is disclosed in copending application Ser. No. 868,982, filed 5-30-86, and assigned to the same assignee, where embedded in or coated on the paper would be microscopic retroreflective spheres which would reflect a separate source of laser emitted light back to a photodetector in a copier, after passing through a filter at the wavelength of the light emitting laser. In both cases the detected signal would be used to interrupt the operation of the copier and/or other uses, such as sounding an alarm or triggering a camera.